We have successfully developed a fully vacuum-sealed CNT x-ray source in a very compact tube without any active
vacuum pump. The brazing process was specially designed and adopted for the vacuum sealing of the x-ray tube at an
elevated temperature. This method enables us to obtain and maintain a desired vacuum level for the reliable electron
emission from the CNT emitters after the vacuum packaging. The CNT x-ray tube also had a novel focusing electrode to
effectively focus electron beams from the CNT emitters on a small area of the anode target, giving a small focal spot of
below 0.3 mm with a large tube current of above 50 mA. The active-current control modulated the CNT x-ray source
digitally with a low voltage of below 5 V and enhanced its stability further. Also, the pull-up circuit positioned at the
cathode node of the x-ray tube shortened the response time down to several micro second. The developed CNT x-ray tube can open up new applications in medical imaging like a stationary tomosynthesis or pulsed fluoroscopy over conventional hot-cathode x-ray sources.